i 20 24 DIGITAL COMMUNICATION LAB MANUAL BECL 504 DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING CITY ENGINEERING COLLEGE
i Communication Laboratory The Communication Laboratory covers design and verification of the concepts of modern digital communication systems that operates from MHz - GHz range. The lab include experiments on applications of Digital coding and modulation techniques, Fiber Optic Commu nication, and Characteristics of microwave waveguide components. This lab is equipped with Oscilloscopes, Function Generators, Modules for Digital Modulation and Demodulation techniques and Power Supply units. To enhance precise measurement and observe waveform with better clarity Digital Storage Oscilloscopes are used. The Microwave test benches are used to conduct experiments in GHz frequency range. Various digital coding and modulation kits are used apart fro m discrete components to demonstrate the basic concepts involved in digital communication. An OFT kit is used to demonstrate communication and multiplexing through Light waves.
ii Digital Communication Lab Semester 5 Course Code BECL504 CIE Marks 50 Teaching Hours/Week (L:T:P: S) 0:0:2:0 SEE Marks 50 Credits 01 Total SEE+CIE 100 Exam Hours 2 Hours Examination type (SEE) Practical Course objectives: This laboratory course enables students to • Design of basic digital modulation techniques using electronic hardware. • Simulation of vector computations and derive the orthonormal basis set using Gram Schmidt procedure. • Simulate the digital transmission and reception in AWGN channel • Simulate the digital modulations using software and display the signals and its vector representations. • Implement the source coding algorithms using a suitable software platform. • Simulate the channel coding techniques and perform decoding for error detection and correction. Sl.NO Experiments Hardware Experiments 1 Generation and demodulation of the Amplitude Shift Keying signal. 2 Generation and demodulation of the Phase Shift Keying signal. 3 Generation and demodulation of the Frequency Shift Keying signal. 4 Generation of DPSK signal and detection of data using DPSK transmitter and receiver. Simulation Experiments (Use MUKU:GO / MATLAB / Scilab /LabVIEW or any other suitable software) 5 Gram - Schmidt Orthogonalization: To find orthogonal basis vectors for the given set of vectors and plot the orthonormal vectors. 6 Simulation of binary baseband signals using a rectangular pulse and estimate the BER for AWGN channel using matched filter receiver. 7 Perform the QPSK Modulation and demodulation. Display the signal and its constellation. 8 Generate 16 - QAM Modulation and obtain the QAM constellation. 9 Encoding and Decoding of Huffman code. 10 Encoding and Decoding of binary data using a Hamming code. 11 For a given data, use CRC - CCITT polynomial to obtain the CRC code. Verify for the cases, a) Without error b) With error 12 Encoding and Decoding of Convolution code
Sl. No. Name of the Experiment 1 Generation and demodulation of the Amplitude Shift Keying signal. 2 Generation and demodulation of the Phase Shift Keying signal. 3 Generation and demodulation of the Frequency Shift Keying signal. 4 Gram - Schmidt Orthogonalization: To find orthogonal basis vectors for the given set of vectors and plot the orthonormal vectors. 5 Simulation of binary baseband signals using a rectangular pulse and estimate the BER for AWGN channel using matched filter receiver. 6 Perform the QPSK Modulation and demodulation. Display the signal and its constellation. 7 Generate 16 - QAM Modulation and obtain the QAM constellation. 8 Encoding and Decoding of Huffman code. 9 Encoding and Decoding of binary data using a Hamming code. 10 Encoding and Decoding of Convolution code.
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE AIM: To design and study the working of ASK modulation and demodulation system with the help of suitable circuit Specifications: M(t) = 10V, 500Hz , C(t) = 5V, 10KHz. COMPONENTS REQUIRED: Sl. No. Item & Specification Quantity 1 Transistor - SL100 1No. 2 uA741 2 No. 3 Resistor - 6.8K 1 No 4 Resistor - 2.2K 1No. 5 Resistor - 22k pot 1 No. 6 Capacitor - 0.01u F 1No. 7 Diode - 1N 4001 1No . THEORY: Amplitude Shift Keying (ASK) is a digital modulation scheme where the binary data is transmitted using a carrier signal with two different amplitude levels. For binary 0 and 1, the carrier switches between these two levels. In its simplest form, a carrier is sent during one input and no carrier is sent during the other. This kind of modulation scheme is called on - off keying. A simple ASK modulator circuit is shown in figure. Here a sinusoidal high frequency carrier signal is sent for logic ‘0’ ( - 5V) and no carrier is sent for logic ‘1’ (+5V). The transistor works as a switch closes when the input (base) voltage is +5V (logic ‘ 1’) and shorts the output. When the input voltage is - 5V (logic ‘0’), the switch opens and the carrier signal is directly connected to the output. The demodulator circuit consists of an envelope detector and a comparator. The diode D selects the positive half cycle of the ASK input. The envelop detector formed by 2.2K resistor and 0.01uF capacitor detects the data out of the ASK input. The Op Amp com parator and the zener diode amplitude limiter convert this detected signal to its original logic levels. The 10K potentiometer may be varied to set suitable reference voltage for the comparator. Expt No - 1 . AMPLITUDE SHIFT KEYING MODULATION AND DEMODULATION
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE CIRCUIT DIAGRAM: EXPERIMENTAL PROCEDURE: 1. Rig - up the modulator circuit as show in the figure. 2. Set the message signal of amplitude 10 V(P - P) and frequency 500 Hz. 3. Set the carrier signal of amplitude 2 V(P - P) and frequency 2 kHz. 4. Observe both the message input and ASK output simultaneously on CRO and plot. 5. Apply the ASK output of the modulator to the demodulator input. 6. Observe both the ASK input and the demodulated output simultaneously on CRO. Adjust the reference voltage of the comparator if needed. 7. Plot the waveforms.
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE OBSERVATIONS: EXPECTED WAVEFORMS: RESULTS : ASK is generated and verified using modulation and demodulation techniques . Time Period Amplitude Messages Carrier Output Signal Demodulated Signal
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE AIM: To study the working of FSK modulation and demodulation with the help of a suitable circuit. Specifications: M(t) = 10V, 500Hz , C1(t) = 5V, 1KHz. C2(t) = 5V, 2KHz. COMPONENTS AND EQUIPMENTS REQUIRED: Sl. No. Item & Specification Quantity 1 Transistor - SL100 , SK100 1No. 2 uA741 2 No. 3 Resistor - 10K 1 No 4 Resistor - 1 .5 k 1No. 5 Resistor - 22k pot 1 No. 6 Capacitor - 0. 1 u F 2 No. 7 Diode - 1N 4001 1No . THEORY: Frequency Shift Keying (FSK) is a digital modulation scheme where the digital data is transmitted using a high frequency carrier signal. For logic ‘0’ and ‘1’ the carrier signal switches between two preset frequencies, hence the name FSK. Binary FSK is a form of constant - amplitude angle modulation and the modulating signal is a binary pulse stream that varies between two discreate voltage levels but not continuous changing analog signal. In FSK, the carrier amplitude (Vc) remains constant with modulation and the carrier radian frequency(wc) shifts by an amount equal to +w/2. The frequency shift is proportional to the amplitude and polarity of the input binary signal. For example, a binary 1 could be +1 volt and a binar y zero could be - 1 volt producing frequency shifts of +delta(w)/2 and – delta(w)/2 respectively. The rate at which the carrier frequency shifts is equal to the rate of change of the binary input signal vm(t). thus the output carrier frequency deviates(shifts) between wc+delta(w)/ 2 and wc - delta(w)/2 at the rate equal to fm. Expt No - 2 . FREQUENCY SHIFT KEYING MODULATION & DEMODULATION
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE CIRCUIT DIAGRAM: EXPERIMENTAL PROCEDURE: 1. Test all the components and probes. 2. Set up the FSK modulator and demodulator circuits on the bread board. Switch on the power supplies. 3. Feed 5V, 100Hz (10Vpp, 100Hz) square wave as the data input. Vary the pot R C to adjust the output frequencies if needed. 4. Observe both the input and output waveforms on CRO and plot. 5. Apply the FSK output of the modulator to the input of the demodulator, and observe the output. Vary the 10K pot to get the PLL locked with the input signal. Plot the waveforms
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE EXPECTED WAVEFORMS: OBSERVATIONS: RESULTS : FSK is verified using modulation and demodulation technique. Time Period Amplitude Messages Carrier Output Signal Demodulated Signal
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE AIM: To Study the operation of PSK ( Binary) modulation & Demodulation and to plot the PSK wave forms for Binary data at different frequencies. COMPONENTS AND EQUIPMENTS REQUIRED: Sl. No. Item & Specification Quantity 1 Transistor - SL100 1No. 2 uA741 3No. 3 Resistor - 10K 5No 4 Resistor - 1k – 1 1No. 5 Resistor - 10k pot 1No. 6 Resistor - 22k pot 2No. 7 Capacitor - 1 0u F 1No. 8 Diode - 1N 4001 1No . THEORY: Phase Shifting Keying (PSK) is a modulating / Data transmitting technique in which phase of the carrier signal is shifted between two distinct levels. In a simple PSK (i.e Binary PSK) un - shifted carrier is transmitted to indicate a 1 condition , and the carrier shifted by 180 o i.e is transmitted to indicate a 0 condition. Wave forms are shown in Figure PSK Modulating & Demodulating circuitry can be developed in number of ways, one of the simple circuit is used in this trainer. Expt No - 3. PHASE SHIFT KEYING MODULATION & DEMODULATION
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE EXPERIMENTAL PROCEDURE: 1. Connect carrier signal to carrier input of the PSK Modulator. 2. Connect data signal say 4 KHz from data source to data input of the modulator. 3. Keep CRO in dual mode. 4. Connect CH1 input of the CRO to data signal and CH2 to the output of the PSK modulator 5. Observe the PSK o/p Signal with respect to data signal and plot the wave forms 6. Compare the plotted waveforms with given wave forms. 7. Connect the PSK output to the PSK input of the demodulator. 8. Connect carrier to the carrier input of the PSK demodulator 9. Note: In actual communication system reference carrier is generated at receiver. 10. Keep CRO in dual mode. 11. Connect CH1 to the data signal (at Modulator) and CH2 to the output of the demodulator. CIRCUIT DIAGRAM:
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE Simulation Experiments (Use MUKU:GO / MATLAB / Scilab /LabVIEW or any other suitable software) 4 Gram - Schmidt Orthogonalization: To find orthogonal basis vectors for the given set of vectors and plot the orthonormal vectors. 5 Simulation of binary baseband signals using a rectangular pulse and estimate the BER for AWGN channel using matched filter receiver. 6 Perform the QPSK Modulation and demodulation. Display the signal and its constellation. 7 Generate 16 - QAM Modulation and obtain the QAM constellation. 8 Encoding and Decoding of Huffman code. 9 Encoding and Decoding of binary data using a Hamming code. 10 Encoding and Decoding of Convolution code
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE 4 Gram - Schmidt Orthogonalization: To find orthogonal basis vectors for the given set of vectors and plot the orthonormal vectors.
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE OUTPUT :
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE 5 Simulation of binary baseband signals using a rectangular pulse and estimate the BER for AWGN channel using matched filter receiver.
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE OUTPUT:
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE 6 Perform the QPSK Modulation and demodulation. Display the signal and its constellation.
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE OUTPUT
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE 7 Generate 16 - QAM Modulation and obtain the QAM constellation.
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE OUTPUT:
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE 8 Encoding and Decoding of Huffman code.
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE OUTPUT: Enter the probabilities: [0.3 0.25 0.2 0.12 0.08 0.05] The huffman code dict: [1] '0 0' [2] '0 1' [3] '1 1' [4] '1 0 1' [5] '1 0 0 0' [6] '1 0 0 1' Enter the symbols between 1 to 6 in[ ]: [3] sym = 3 The encoded output: 1 1 Enter the bit stream in[ ]; [1 1] The symbols are: 3 Entropy is 2.360147 bits Efficiency is:0.991659
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE 9 Encoding and Decoding of binary data using a Hamming code.
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE OUTPUT:
Digital Communication Lab Manual - BECL504 Dept of E&C, CITY ENGINEERING COLLEGE 1 0 Encoding and Decoding of Convolution code OUTPUT: Message Sequence: 1 0 1 1 0 Encoder output: 1 1 1 0 0 0 0 1 0 1 Decoder output: 1 0 1 1 0